The present invention relates to the field of cataract surgery, and, more particularly, to the insertion of an artificial intra-ocular lens into the eye, following such surgery.
A cataract is a clouding of the natural lens, the part of the eye located behind the cornea, and behind the aqueous humor. The natural lens is encapsulated within a membrane, the posterior portion of which forms a boundary between the aqueous and vitreous humors. The lens focuses light on the retina, on the rear wall of the eye, for transmission to the brain. When the clouding of the natural lens become severe, the patient can no longer see through that eye, and the cataract must be removed.
Various procedures have been known in the field of cataract removal. The earliest techniques required a large incision in the cornea. In the so-called intra-capsular procedures, so designated because they involved removing the entire natural lense and membrane encapsulating the lens, it was necessary to make an incision extending along a 180.degree. arc around the cornea. The natural lenses would then be extracted, by cryogenic freezing and surgical removal, or by other means. The large incision needed to perform this surgery increased the risk, discomfort, and convalescence time associated with the operation.
Eventually, other techniques were developed which reduced the size of the incision necessary for removal of the cataract. In the so-called extra-capsular procedure, an incision of the order of 11-13 mm was made in the cornea, and the hard nucleus of the cataract was forced out of, or "expressed" from, the eye by gentle application of pressure. With this procedure, it became possible to preserve the posterior portion of the soft membrane, thereby maintain a separation between the aqueous and vitreous humors.
The procedures requiring an 11-13 mm incision were an improvement over the older techniques, but still engendered a certain amount of discomfort and risk. Eventually, a new technique for cataract removal, known as phacoemulsification, was developed. In this procedure, a hollow, vibrating needle and infusion sleeve are inserted into a small incision in the eye, the incision being only about 3 mm long. The needle vibrates at an ultrasonic rate, and the vibration causes the cataracted natural lens to be emulsified into tiny pieces. The remains of the natural lens are then drawn out by suction.
Removal of the clouded natural lens is only half of the solution for a cataract patient. The natural lens serves a vital purpose, namely the focusing of images of the retina. The natural lens has a refractive power of the order of about 19 diopters, so a person whose natura lens has been removed needs a powerful artificial lens to compensate for the missing lens. In the past, it was necessary for cataract surgery patients to be obliged to wear extremely thick eyeglasses for the rest of their lives.
Dissatisfaction with the use of these thick eyeglasses led to a search for an artifical intra-ocular lens (IOL), which could substitute for the natural lens. Many varieties of IOLs, and methods for their insertion and storage, were devised. Examples of IOLs in the patent literature are given in U.S. Pat. Nos. 4,122,556, 4,249,271, 4,251,887, 4,253,199, 4,298,994, 4,446,581, 4,449,257, 4,463,457, 4,468,820, and 4,490,860. Other references dealing with insertion methods for IOLs are U.S. Pat. Nos. 4,198,980, 4,214,585, and 4,349,027. U.S. Pat. Nos. 4,423,809 and 4,257,521 deal with packaging systems for IOLs.
The phacoemulsification process is very advantageous because of the extremely small incision required. But this advantage has, in the past, been surrendered when the time comes for insertion of an IOL Most IOLs require incisions having a length of about 6.5-8.0 mm, which means that the 3 mm incision made to perform the phacoemulsification needs to be enlarged by a factor of at least 2. It has therefore been necessary to enlarge the wound made during the cataract removal operation, before inserting the IOL.
The above-described problem has been partially solved with the introduction of flexible IOLs. Such IOLs are described in an article in IOL & Ocular Surgery News, Vol. 1, No. 14 (July 15, 1983), entitled "News Lens Allows Insertion in 3 mm Wound". The IOL is constructed of silicone, and can be folded, so that it can be inserted into a 3 mm incision.
Despite the introduction of flexible IOLs, there is still lacking a reliable and simple method of inserting such a lens. The present invention solves this problem, by providing an apparatus and method for IOL insertion, which is relativey easy to perform, and which requires no larger incision in the eye than that required for the phacoemulsification process. In short, the present invention makes it possible to exploit fully the advantages of phacoemulsification, by providing a simple, safe, and minimally traumatic means of inserting a flexible intra-ocular lens.